1. Field of the Invention
The present invention relates to a canister arrangement in a power generating apparatus and more particularly to an arrangement of a canister containing an adsorbent for adsorbing fuel that evaporates from an engine fuel tank.
2. Description of the Related Art
Japanese Publication No. JP 7-34985 describes a conventional device having a canister containing an evaporative fuel adsorbent. The device described in JP 7-34985 includes an engine, a fuel tank for storing fuel to be supplied to the engine, and a canister containing an adsorbent for adsorbing fuel that evaporates from the fuel tank. The canister includes a communicating tube, which places the canister in communication with the atmosphere. The canister is also in communication with an intake system of the engine.
The engine is driven by fuel supplied from the fuel tank and outputs a driving force of a predetermined magnitude. During this operation, the adsorbent and the canister containing the adsorbent therein generally work as follows. Fuel vapor is roughly constantly produced in the fuel tank. During a period in which the engine is stopped or in a low-speed range as in idling, most of the fuel vapor is adsorbed by the adsorbent, thereby preventing the fuel vapor from being released into the atmosphere.
When the engine is in a medium-speed or high-speed operating range, a negative pressure builds up inside the intake system of the engine. The negative pressure causes atmospheric air to be sucked into the canister through the communicating tube of the canister. The fuel vapor that has been adsorbed onto the adsorbent is purged from the adsorbent by said sucked air and flows along with the air into the intake system, where it is supplied to the engine and subjected to combustion.
When the adsorbent is left unused for a long period of time with the fuel vapor adsorbed thereonto, or when the fuel vapor is repeatedly adsorbed onto and purged from the adsorbent a number of times, the capability (e.g., usable life) of the adsorbent decreases, and a purge rate (purge characteristics) on the fuel vapor decreases.